Effectiveness of thermal therapy in post trauma and post surgical settings continues to engender a variety of thermal therapy systems. (The term "thermal therapy" for purposes of this document means therapy which induces hypothermia or hypothermia, cold or heat, to the body or a part of it, whether extradurally or otherwise.) The precise mechanics of thermal therapy remain the subject of debate and research. The literature indicates that cold therapy can, for instance, reduce swelling, inflammation, edema and ischemic damage due to vascular or arterial compromise. Cold therapy is also said as a general matter to aid in control and management of tissue hypoxia that can otherwise be a manifestation of impaired oxygen diffusion or compromised circulation. It also is generally recognized to reduce pain and reduce the need for pain relief medication.
Recent developments in thermal therapy systems include patient portable systems which employ a small ice chest connected to a flexible heat exchanger or thermal therapy pad via a pair of tubes. A pump, which may be located in the ice chest, supplies chilled fluid to an inlet port of the pad. An exhaust port connected to an exhaust tube carries the fluid, or a portion of it, in a return loop to the ice chest. Temperature within the pad may be regulated in a number of ways. A valve may be employed to control the flow rate in the pad inlet or exhaust, and/or to recirculate a portion of the exhaust fluid.
In physical therapy, as in many things, effectiveness of treatment is largely a function of convenience and comfort. Portable thermal therapy systems accordingly enjoy increased popularity to a major degree because their increased convenience promotes the patient's actually adhering to the therapy program. Such systems, for instance, eliminate the need constantly to replenish an ice pack with a new supply of ice, endure the chore of a weighty and cumbersome ice pack on the knee or shoulder, and the added bother of interposing a towel, with its inevitable sogginess, to mediate between the freezing ice cubes and the skin. Conventional thermal therapy systems instead use a thinner, lighter, flexible pad with a reasonably but not overly cold temperature. The patient may carry the ice chest with its own battery pack in order to supply circulation of the chilled fluid to the pad, or when able to access an electrical outlet, rely on the power grid using a power converter.
Because efficacy of physical therapy and cold therapy in particular is largely a function of convenience, conventional thermal therapy systems present significant additional potential for improvement and design breakthroughs. Because patients tend to abandon the course of thermal therapy treatment if it is inconvenient or uncomfortable, it is critical to ensure that the flexible therapeutic pad of such systems is comfortable to the patient, promotes convenience, and is minimally intrusive to the patient's flexibility and mobility. Patients will be inclined to discontinue the therapy if the pad, for instance, overly restricts mobility of the joint, must be continually reapplied, requires undue attention and readjustment, feels uncomfortable, or is otherwise cumbersome, awkward or inconvenient.
On another more immediate level, effectiveness of the heat transfer imparted by the flexible therapy pad may suffer if a thermal therapy pad becomes occluded as it is placed on the joint or as it flexes with the joint. Some conventional pads are shaped in a manner that causes internal blockage when placed on the joint or as the knee or shoulder flexes; such blockage restricts fluid flow in at least parts of the pads and thus deprives portions of the body surface of effective thermal therapy. Moreover, some conventional pads lose contact with areas of the skin when initially placed on the knee or shoulder or when the knee or shoulder is flexed and the pads fail effectively to conform to the body surface through the appropriate range of flexion. Accordingly, increased flexibility of the therapy pad must not be undertaken at the expense of effective heat transfer.
Previous flexible therapeutic pads employed in cold therapy systems recognize the value of a thinner pad per se but they generally adhere gratuitously to notions of symmetry. For instance, the pad disclosed in U.S. Pat. No. 5,086,771 issued Feb. 11, 1992 to Molloy and U.S. Pat. No. 5,417,720 issued May 23, 1995 to Mason, are symmetrical about their center axis. Although symmetry appeals intrinsically to the intellect, the present invention does not blindly bow to or adopt symmetry in flexible therapeutic pad topology. In that respect, U.S. Pat. Nos. 5,411,542 issued May 2, 1995 and 5,470,353 issued Nov. 28, 1995 to Jensen show asymmetrical thermal therapy pads, but in a way specifically tailored to the ankle and shoulder joint, respectively. Such specialized pads can provide comfort, convenience and more effective heat transfer through a better fit, but requiring separate pads for the ankle and shoulder presents added design, manufacturing, distribution, inventory and tracking expense because, among other things, a number of different pad designs must be supported throughout this entire chain rather than a single pad design which can accommodate various joints.
Conventional flexible therapeutic pads as described in the Mason and Molloy patents feature inlet and exhaust ports on the center line about which the pads are symmetrical. It is a given that the inlet and exhaust tubes to which the ports are connected must be oriented, for purposes of convenience, generally on the limb, such as for instance, either up the limb or down it, in order to avoid cantilevering the tubes into mid-air and subjecting them to physical interference, inconvenience, excessive wear and abuse. The axis of symmetry of the conventional multijoint pads being aligned with the tubes requires these conventional symmetrical pads to extend continuously and uninterrupted along the proximal/distal axis across the patella or shoulder joint. Flexure of the knee or shoulder causes buckling of such a pad along its center line. The buckling of such pads and concomitant failure effectively to conform to the limb as it flexes can not only cause internal occlusion or blockage within parts of the pad to obstruct fluid flow and render at least a part of the pad ineffectual for thermal therapy; it can also naturally separate the heat exchanger from the body to reduce effectiveness of the cold therapy, create discomfort, and introduce resistance to joint flexure and mobility.
Pads of the present invention, by contrast, feature at least two members which are adapted in shape to conform to body parts that surround the knee, shoulder or other joint, but which members are in fluid communication via a conduit whose centerline does not overlie the patella or the top of the shoulder, or which is not substantially centered on the patella as the joint flexes. Centering of the conduit to one side of the patella or top of the shoulder, the inventors have found, makes a substantial difference in providing flexible fit, form and function without compromise of effective fluid flow in all areas of the pad and consequent effectiveness of thermal therapy imparted by the pad. Positioning the conduit that connects these members may be carried out, for example, by introducing, according to the present invention, gaps, clefts or other peripheral discontinuities which could, for example and if desired (but not necessarily), overlie and intersect the limb proximal/distal axis in order to increase flexure of the pad without compromising other value properties.
The present invention also exploits the opportunity to optimize flow velocity at predetermined points within a flexible therapeutic pad, unlike conventional pads, in order to accentuate local heat transfer rate where appropriate. The inventors believe, and their experiences tend to show, that they can adjust and create flow restrictions at desired points within the pads in order to regulate local flow velocity and affect heat transfer rate where the knee or shoulder needs it. For instance, the inventors believe that increasing local flow velocity closer to the interior of the pad as a general matter can promote a greater heat transfer rate at the site of injury or surgery, with reduced heat transfer at the perimeter of the site. Such variable heat transfer rates can be particularly useful in applications where inflammation, edema, ischemia and/or swelling is local in nature.